Multian V. Quadratic and cubic nonlinear optical responses of ZnO har-monic nanoparticles and KDP single crystals with incorporated metal oxides nanoparticles.

In this work the analysis was performed of optical and nonlinear-optical proper-ties of harmonic nanoparticles - a new class of biological markers, and composites based on KDP single crystals with incorporated metal oxide nanoparticles under CW and pulsed laser excitation. Third harmonic generation (THG) efficiency measurements within interface scan-ning technique for the ZnO NPs colloidal suspensions under ns range laser pulses excitation at 1064 nm were performed. For the ZnO NPs with mean sizes 40–150 nm it was obtained characteristic spatially averaged 〈χZnO(3)〉 ~10-10 esu. It was shown that obtained THG efficiencies are increasing with growth of NPs size and exceeding values for bulk ZnO; estimated data are in a good agreement with data from hyper-Rayleigh scattering measurements technique and with the reference data for bulk ZnO. The proposed technique can be applied for nondestructive express diagnostics of NPs colloidal suspensions after synthesis stage in order to characterize the nonlin-ear optical properties of harmonic nanoparticles, studying the impact of their size and shape. Characterization of synthesized ZnO NPs, which was deposited from colloidal suspensions of various solvents, was carried out by the self-action of ps laser pulses at 1064 nm. It was shown that the efficiency of the refractive and absorptive NLO responses depends on the type of solvent used for the synthesis of NPs. It was demon-strated that different types of solvents used for the NPs synthesis change the SHG efficiency under fs laser pulses excitation at 800 nm. For the analysis of NLO response enhancement mechanisms of ZnO NPs, spectral analysis was performed and the NLO properties of ZnO single crystals with a differ-ent defect content were studied. It was shown that there is a correlation between the values of the real and imaginary parts of the cubic NLO susceptibility with the data of PL and IR spectroscopy in the area of defective bands, the efficiency of elastic optical scattering - with the concentration of defects. The efficiency of second-harmonic generation (SHG) in KDP single crystals with incorporated metal oxides NPs has been studied. In particular, it was shown that the incorporation of TiO2 nanoparticles increases the efficiency of SHG in KDP:TiO2 crystals by 60% and 35% for pyramidal/prismatic growth sectors under fs laser ex-citation at 800 nm. In KDP:NOA with a nanostructured oxyhydroxide of aluminum (NOA) nanofibers, an increase in the order magnitude of SHG efficiency was ob-tained in comparison with a nominally pure KDP crystal under ns pulsed excitation at 1064 nm. The prototype of the device for analyzing the cross section of the elastic optical scattering indicatrices under continuous laser excitation was designed. The device was tested on a wide class of objects, in particular for nominally pure KDP single crystals, it was shown that the elastic optical scattering losses at 1064 nm is lower than for KDP:TiO2 crystals with incorporated TiO2 NPs due to the lower concentra-tion of uncontrolled impurities. It was shown that optical scattering losses in a KDP:NOA single crystal depends on NOA nanofibers concentration. For ZnO single crystals, high optical scattering sensitivity to defect content was shown due to high polarizability of defective states and an effective refractive response of photoinduced delocalized carriers.